Step 2

Preheat the oven to 400 º F; grease a 2.5-liter casserole dish with butter and set aside.

Step 3

Add the potato to a medium saucepan and cover with cold water by 2 inches. Put the lid on the saucepan and bring it to a boil, and then uncover and cook until the potatoes are tender, about 8 minutes, reducing the heat slightly as necessary so the potatoes don’t boil over. Drain the potatoes well, return them to the pot, and mash them with 2 tablespoons butter, the milk, salt, and pepper.

Step 4

While the potatoes cook, heat 2 tablespoons butter in a large skillet over medium heat; add the onion and cook until softened, but not browned, about 6 to 8 minutes, stirring occasionally. Add the garlic and kale and cook until the kale is wilted, about 1 to 2 minutes, stirring constantly.

Step 5

Stir the kale mixture into the mashed potatoes and transfer to the prepared casserole dish; sprinkle the cheddar on top.

Step 6

Bake until the cheese is melted and golden, about 10 minutes (you can turn on the broiler to help it brown faster, but watch it closely).

Step 7

Serve.